Shimano Dura-Ace 9070 Di2 Groupset
- Dura-Ace 9070 Shift & brake lever set
- Dura-Ace 9070 Front derailleur
- Dura-Ace 9070 Rear derailleur
- Dura-Ace 9000 Crankset 172.5mm with 52/36 rings
- Dura-Ace 9000 Brake set
- Dura-Ace 9000 11-28 cassette
- Dura-Ace chain
- e-tube wiring kit with junction A & B boxes
- Internal battery and charger
The general benefits of Shimano's Di2 shifting are legion, but the one that bears mentioning for anyone who hasn't had the opportunity to ride it is the ability to shift under full power. Of course, the engineers at Shimano can't just expect to roll out the same group with a new number. And they apparently don't. Some overall system changes from 7970 to the current 9070 include the ability to program each button of the myriad options of shifting controllers to operate either derailleur.
The shift levers at the head of the group have seen, arguably, the biggest redesign. The best part of this is definitely the ability to run through the entire cassette with one shift movement. Once programmed through the E-Tube software, one sustained motion will take you all of the way up or down the cassette. Finally. They're also 18 grams lighter than the previous 7970 shift levers and the whole shifter is more svelte, getting slimmer at the hoods and longer at the levers.
A few other changes are worth noting, if not exactly earth shattering. Shimano has narrowed the crevice between lever and hood, nearly eliminating the possibility of road grime getting in there, which was one of our only complaints with the 7970 levers. You can also now select five different shifting speeds for the rear derailleur. Most of us probably won't take advantage of this, but it's the kind of customizable ride quality that someone would expect from a luxury, top-end group.
The rear derailleur also wins big with E-tube software, letting you adjust the tuning in each position with the precision of the legendary mechanics of the peloton. It also runs diagnostics on itself, so it can identify any user errors during installation or bumps taken while riding. This is nice, because we certainly aren't legendary mechanics. One last feature that makes us chuckle now but may pay dividends later is that the derailleur can move itself out of harm's way in the event of an in-saddle user error. The front derailleur gets similar benefits minus the instinct for self-preservation and also features an auto-trim to eliminate chain rubbing and dropping.
The crankset, the gorgeous, mechanical heart of this electronic group, is taken straight from the Dura-Ace 9000 group and features the lightweight and improved stiffness of a four arm spider. The Hollowtech II and Hollowglide technologies that underwrite these qualities involve strategic distribution of hollow aluminum throughout the crankset and chainrings for an unrivaled weight-to-stiffness ratio.
The cassette, brakes, bottom bracket, and chain are also the same as the mechanical Dura-Ace. The cassette uses titanium for cogs that are 16 teeth and larger, and its 11-28t range will save your knees on high grades but won't spin out if there's any advantage to be gained by pedaling on descents. The brakes produce 10% more rim grabbing power than their predecessors while accommodating up to 28mm tires, and the bottom bracket's new sealing system results in a 50% reduction in drag without compromising bearing protection.
The hollow-pin chain warrants some extra attention after all, it's the spine of your drivetrain. It incorporates Shimano's Sil-Tec treatment to reduce friction. Fluorine particles embedded in the chain's surface result in a claimed 60% less rotational sliding friction, 2.7 fewer decibels of chain noise, 30% more mud and debris clearing, and a 20% longer wear life than chains with zinc-nickel plating.
Finally, those brakes. The Dura-Ace brakes were tested and tested and tested until the engineers were practically in an insane asylum, and the result, powerful but easily-controllable brakes, able to scrub speed effortlessly and with complete control, with virtually no heat fade, even in extreme conditions.
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